1. Field of the Invention
The present disclosure relates generally to modular packet switch/router design and operation, and more particularly to internal power distribution for such devices.
2. Description of Related Art
Many packet switches/routers (hereinafter “switches”) are designed in a modular fashion, with exchangeable cards and modules. The heart of such a system is a backplane with signaling connectors for each available card slot, e.g., the exemplary backplane 100 of FIG. 1. Backplane 100 contains internal interconnections that route signals and primary power to a large number of external connector blocks. Two signal connector blocks RPSC0, RPSC1 provide connections for switch management cards. Fourteen signal connector blocks (LCSC1, LCSC14 are exemplary) provide connections for line cards, which provide external ports for receiving and transmitting the packets switched through the switch. Nine signal connector blocks (SFSC1, SFSC9 are exemplary) provide connections for switch fabric cards, which actually pass packets between the line cards.
In addition to supporting signaling between the cards, backplane 100 distributes primary power to each attached card from two redundant banks of power supplies (not shown). One power supply bank supplies 48 V “A” power to a connection point 110A, and the other power supply bank supplies 48 V “B” power to a connection point 110B. Power is transferred through the backplane to “A” and “B” power connector blocks (LCPC1A and LCPC1B, adjacent signal connector block LCSC1, are exemplary) located adjacent the signal connector blocks.
FIG. 2 shows backplane 100, partially populated with three switch fabric cards SF5, SF6, and SF7, and two line cards LC11, LC13, as a system 200. Each card uses DC/DC power converters to convert the 48 V distribution power received through the backplane to lower voltages (e.g., 3.3 V down to 1.0 V) required by the various logic and memory devices present on each card. For instance, switch fabric card SF7 is depicted with two DC/DC power converters PC7-1, PC7-2 that supply power at two different low voltages to the logic and memory devices present on that card. Line card LC13 (which actually is a combination of two cards, logic board LB13 and port interface module PIM13) is depicted with four DC/DC power converters PC13-1, PC13-2, PC13-3, PC13-4 that supply power at four different logic voltages to the logic and memory devices present on the logic board and the ports (e.g., port device P13-1) present on the port interface module.
FIGS. 3 and 4 show the general direction of power flow in the FIG. 2 system. Referring first to FIG. 3, backplane 100 is shown without any cards inserted. Two four-ounce copper power planes (not visible) within backplane 100 connect 48 V A primary power from connection point 110A to each “A” power connector block (connector block LCPC1A is exemplary). Two other four-ounce copper power planes (not visible) within backplane 100 connect 48 V B primary power from connection point 110B to each “B” power connector block (connector block LCPC1B is exemplary). Primary power flow direction within the backplane is indicated generally by the groups of overlaid heavy arrows 48VA and 48VB.
FIG. 4 shows backplane 100 in side view, with a line card LC13 and a switch fabric card SF7 visible. 48V power distributed by the backplane reaches connector blocks SFPC7A and SFPC7B, where the power is transferred to internal power planes (not visible) within switch fabric card SF7. These power planes deliver primary power to DC/DC power converters PC7-1 and PC7-2, which convert the primary power to two logic voltages LV. Power at logic voltages LV is then distributed on other internal power planes (also not visible) within switch fabric card SF7 to logic and memory located on SF7. 48V power distributed by the backplane also reaches connector blocks LCPC13A and LCPC13B, where the power is transferred to internal power planes (not visible) within logic board LC13. These power planes deliver primary power to DC/DC power converters PC13-1 to PC13-4, which convert the primary power to four logic voltages LV. Power at logic voltages LV is then distributed on other internal power planes (also not visible) within logic board LB13 and port interface module PIM13.